Who is Participating?

these informations are actually provided in google's dev guide, you probably over looked them so here they are:
1) "The feedUri value is typically http://www.google.com/calendar/feeds/default/private/full for working with your primary calendar"
2) "Create a new CalendarService instance, setting your application's name (in the form companyName-applicationName-versionID). "
3) you need to call "service.setUserCredentials()" with the right usernames and password before calling "Query". You probably need to double check your login info (remember to include the full user name including the domain name).